Treating oil distillates



Patented Dec. 29, 1942 UNITED STATES PATENT OFFICE TREATING OIL DISTILLATES- William W. Reed, Hammond, Ind, 'ass'i'gnor to Socony-Vacuum Oil Company, Incorporated;

New York, N. Y., a corporation of New York Application July 25, 1941, Serial No. 404,013

3 Claims.

This invention is directed to the treatment of distillate petroleum oils with aqueous alkaline reagents, and is specifically directed to a process for such treatment wherein an efiective and complete use of such reagent may be made with a minimum of difiiculties from the formation of emulsions, carryover of reagents into finished oils, and incomplete utilization of reagents.

It has been the practice for a considerable period to accomplish the removal of objectionable materials such as sulphur, color bodies, and the like from distillate petroleum oils by washing with aqueous caustic alkalies, particularly near the point at which the distillates are first condensed from the vapor form. A very usual practice is the introduction of caustic solution at a point near the exit from the condensers from whence the solution and distillate flow in company to the receiver drum or look-box, to be separated therein. This has obvious objections from the standpoint of difiiculty in securing adequate contact of oil and caustic, resulting in incomplete treatment and ineffective utilization of reagent. In other forms a vertical scrubbing drum is installed in the rundown line between condenser and receiver, with or without internal packing or bafiles, in which the distillate enters near the bottom and reagent near the top. With such counterflow somewhat better treatment and reagent utilization may be gotten but there still persist difiiculties with emulsion formation and. carryover of reagent arising from that and from other causes. Even the best forms of this operation, wherein the contacting is carried out in such a tower in the interstices of a packing material, still give rise to such carryover difiiculties as to require the passage of the oil, before discharge from the scrubbing treatment, through a porous body of adsorptive or similar packing material for resolution and removal of reagent.

This invention is based upon the discovery that by a particular system involving both countercurrent and concurrent flow principles, that a most complete utilization of reagent may be achieved and that with a minimum of difficulties from carryover, emulsions, and the like. This is believed to be due to that principle, which is novel, of contacting, in countercurrent, with fresh caustic reagent, a distillate which has been previously contacted, in generally concurrent flow, with reagent from the first mentioned treating step. While not limiting the invention by any theory of operation, it would appear that the pretreatment of the distillate with a partially exhausted reagent tends to take the edge from the distillate in such fashion as to suppress almost entirely the formation or. emulsions and similar difii'culti'e'sformerly experienced. This method also allows for an excellent utilization gram form, we find kerosene vapors, from a distillation operation, on their way to condenser I through pipe 2. Into these vapors, by way of pipe 3, at a point prior to their entry to condenser I, there is introduced a partially spent aqueous alkaline reagent, such as a solution of caustic soda, caustic potash, sodium carbonate, or the like, from a source later described. The caustic reagent so introduced commingles with and flows concurrently with the vapor and condensate therefrom through the condenser l and into vessel 4, wherein the oil and aqueous caustic separate and in which there is maintained a substantial amount of caustic solution through which the oil must pass countercurrently to accumulate at the top of the vessel 4. Spent caustic reagent is withdrawn from the bottom of this vessel by pipe 5 and accumulated oil is withdrawn by pipe 6, the vessel being maintained completely filled. Vessel 4 is preferably without internal baffles or packing, it having been found to operate better this way, although some relatively simple bafiling system is acceptable.

The oil withdrawn by ,pipe 6 from vessel 4 passes into the bottom of vessel 1, wherein there is a packing material, such as Raschig rings, or the equivalent, designated by 8, supported upon a grid 9. Fresh caustic solution is supplied to vessel 1 by pipe [0 in such quantities as to maintain a level of reagent therein at some point ll near to or above the top of the packing 8. In passing upwardly through this caustic reagent, countercurrently, in the broken path afforded by interstices in the packing material 8, the kerosene is efiectively contacted with and treated by the caustic reagent. Partially spent caustic is withdrawn by pipe H! from the bottom of vessel 1 and forced by pump l3 through pipe 3 to be introduced into the uncondensed vapors. Finished kerosene, collecting in the top of vessel I, which is maintained completely full, is withdrawn to storage by pipe I4.

The process so disclosed has been found to operate with excellent results and with a minimum oi difficulties and wastage of reagent. This is ascribed to the principle of contacting the oil at its most highly reactive condition with a partially spent caustic reagent, in not attempting to secure too rigorous a treatment of the kerosene upon its first contact with reagent, and in finally rigorously treating a partially treated kerosene with an active, fresh, caustic reagent.

I claim:

1. That method of caustic scrubbing a petroleum distillate oil comprising the steps of introducing a partially spent aqueous caustic reagent to the vapors of a petroleum distillate oil to flow concurrently therewith to and through condensa-v v tion, separating caustic reagent and condensate oil to form a body of reagent through whichcondensate oil passes upwardly to collect thereabove, removing spent caustic reagent from said pool passing collected partially treated condensate oil from the separation step to and upwardly through the interstices of a packing material submerged 5 in a body of caustic reagent for final treatment, collecting and removing finished oil from above said caustic reagent body, supplying fresh caustic reagent to the top of said caustic reagent body and removing partially spent caustic from the bottom thereof to supply the partially spent caustic first introduced to the oil vapors.

2. That method for the treatment of light distillate petroleum products comprising countercurrently contacting a fresh aqueous alkalinereacting reagent with a petroleum distillate which has previously been concurrently contacted, while being condensed from vapor, with partially spent alkaline reagent withdrawn from the first named treating step.

3. A method-for treating petroleum distillates of the nature of gasoline and kerosene with aqueous alkaline solutions which consists of contacting condensed distillate with fresh alkaline reagent to effect a rigorous treatment and using partially spent alkali from this step for partially treating the vapors of said distillate prior to and during their condensation.

WILLIAM W. REED. 

